JPH09135187A - Tuner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reflection damping factor of tuner with a little components. SOLUTION: This tuner has one signal processing branch at least for performing the frequency selective reception, amplification and/or frequency conversion of RF signal through a wide band input amplifier 1 and a switching step 3 for adding the RF signal to be supplied from an input part 26 through an input amplifier 25 to any arbitrary one signal processing branch. Respective signal processing steps are respectively provided with filter steps 4, 5 and 6 connected to the switching step 3, controllable amplifier steps 7, 8 and 9 arranged next to the filter steps 4, 5 and 6 and mixer steps following the controllable amplifier steps 7, 8 and 9 and the output parts of these mixer steps are connected through a signal connection part to a common output branch.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a tuner.

[0002]

2. Description of the Related Art European Patent Publication No. 95 105 797.5-222
No. 1 describes a tuner with at least two signal processing branches for frequency selective reception, amplification and / or frequency conversion of RF signals. The tuner includes a switching stage that allows an RF signal, which may be supplied from the input, to optionally pass through one of the signal processing branches. Each signal processing branch is
It comprises a filter stage connected to the switching stage, a controllable amplification stage arranged following the filter stage and a mixer stage following the amplification stage. The output of the mixer stage is connected to the common output branch via the signal combiner.

The tuner described above reduces manufacturing costs and allows smaller capacities.

[0004]

On the one hand, a further reduction of noise, ie an improvement of the signal-to-noise ratio, is desired, and on the other hand, if the mixer stage is directly connected to the (controllable) amplifier stage of the signal processing branch, It has been found that the return loss of the treatment branch is reduced. Through the input, the backscatter signal is
There is a risk of reaching the antenna connected to this input, which causes uncontrollable interference.

The object of the present invention is the above-mentioned European Patent Publication
It is to improve the return loss of the tuner with a small number of components without compromising the advantages of the tuner described in 95 105 797.5-2221.

[0006]

According to the invention, it is the object of the present invention to provide at least one signal processing branch for frequency selective reception, amplification and / or frequency conversion of RF signals by means of a wide band input amplifier, and said input amplifier. A switching stage capable of arbitrarily passing an RF signal, which can be supplied from an input via one of the signal processing branches, to one of the signal processing branches, each signal processing branch being connected to the switching stage. A filter stage, a controllable amplification stage arranged subsequent to the filter stage, and a mixer stage following the amplification stage, the output of the mixer stage being connected to a common output branch via a signal coupling unit. It can be solved by a tuner characterized by being connected.

According to the invention, said object is input via at least one signal processing branch for frequency selective reception, amplification and / or frequency conversion of RF signals by means of a wideband controllable input amplifier and said input amplifier. A switching stage capable of arbitrarily passing an RF signal that can be supplied from one of the signal processing branches to one of the signal processing branches, each signal processing branch having a filter stage connected to the switching stage. , With a mixer stage,
It can also be solved by a tuner characterized in that the output of the mixer stage is connected to a common output branch via a signal combiner.

European Patent Publication 95 105 797.5-2
According to the conventional configuration principle so far, No. 221, each signal processing branch has a first filter stage, a controllable amplification stage, a subsequent filter stage, and a frequency reduction of the supplied RF signal. It has a mixer stage for converting. The controllable amplification stage is used for noise reduction of the RF signal before selection in the next filter stage. The gist of the present invention achieves this noise reduction, i.e. improvement of the S / N ratio, by a wide band input amplifier. Especially when the tuner according to the invention is used in a video recorder, this is a very simple and low-cost arrangement. The reason is that a wide band input amplifier of the type described is already present in the antenna input stage of the video recorder which causes the RF signal to loop to the next television receiver (monitor). Therefore, the desired noise reduction is achieved without any additional components.

The wideband input amplifier also reduces crosstalk, especially of the power oscillating signal, because it downconverts the RF signal in the mixer stage. The effects of such backscatter,
Particularly, the influence of oscillation from the mixer stage to the antenna is particularly preferable when the filter stage is not directly arranged before the mixer stage of the signal path for the RF signal of the signal processing branch. The present invention can reduce this backscattering effect to a minor degree without any additional means. In particular, the semiconductor integration of the controllable amplification stage and the mixer stage can be realized without any inconvenience in signal processing operation.

In conventional tuners, the desired impedance matching between the antenna terminal connected to the input and the filter stage of the tuner is achieved by placing a (controllable) amplifier stage in the head of the signal processing branch. Be satisfied. Also, this impedance matching can be conveniently realized without any additional components by the wideband input amplifier arranged according to the invention.

Furthermore, the tuner of the invention makes it possible to dispense with a separate first filter stage between the input and the (controllable) amplifier stage, which protects the (controllable) amplifier stage from intermodulation. .

According to the invention, the wideband input amplifier has a fixed gain factor and the amplifier stage following the mixer stage of each signal processing branch has a controllable gain factor, or the wideband input amplifier is adjustable. Having a gain factor, a separate amplification stage following the mixer stage can be omitted in the signal processing branch. Also, if desired, the wideband input amplifier can have at most a constant gain factor. The solution with a wideband controllable input amplifier offers a very simple construction, which is particularly suitable for implementing standardized tuners. Wideband controllable input amplifiers can be used especially for amplification or power control.

If the wideband input amplifier has a constant gain factor, the controllable amplification stage of the signal processing branch can be used for amplification or power control. This configuration is suitable for simplifying the configuration of the antenna input stage for the video recorder for amplitude or power control to be performed in the signal processing branch.

According to the tuner of the present invention, the mixer stage of the signal processing branch is preferably connected to a common oscillator generator comprising a common phase locked loop and a separate oscillation stage for each signal processing branch. Preferably, each signal processing branch is realized for a preset frequency range (band). An oscillation stage is provided for each band, but a phase-locked loop is provided for all bands. As a result, the synchronization between the filter stage and the oscillator in each signal processing branch can be simplified.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment of the tuner shown in FIG. 1, a wideband input amplifier 1 having an input section connected to an RF signal input section 2 and an output section connected to a switching stage 3
And three signal processing branches following the switching stage 3 and forming the end of the signal coupling section. In FIG. 1, each signal processing branch is represented by a filter stage 4, 5 and 6 connected to a switching stage 3.
, And controllable amplification stages 7, 8 and 9 connected to the filter stages 4, 5 and 6, respectively, and mixer stages 10, 11, 12 connected to the associated controllable amplification stages 7, 8 and 9, respectively. RF
The signal is fed from the input section 2 to the wideband input amplifier and the switching stage 3.
Is optionally supplied to one of the signal processing branches. In the signal processing branch, the desired frequency band associated with the signal processing branch is selected by the filter stages 4, 5, 6.
The mixer stages 10, 11 and 12 receive the filtered RF signals in the frequency band only via the controllable amplification stages 7, 8 and 9 and down-convert the frequencies in the mixer stages 10, 11 and 12. In the arrangement of FIG. 1, node 13
The signal combiner composed of the output amplifier 14 and the output amplifier 14 can supply the down-converted RF signal to the common output 15. Optionally, the signal combiner may also comprise only nodes, in which case the output amplifier 14 as well as the output 15 are associated with a common output branch for all signal processing branches.

A phase-locked loop 16 common to all signal processing branches and a separate oscillating stage 17, 18 for each signal processing branch to generate the oscillations required to downconvert the RF signal. , 19 are used in the arrangement shown in FIG. Phase locked loop 16
And oscillation generators 17, 18 and 19 are connected to each other in a known manner. In order to eliminate the interference between the signal processing branches, the oscillating stages 17, 18 and 19 are arbitrarily switched on and off via the data leads 20 so that the oscillating stages 17, 1
8 and 19 can only oscillate by connecting the signal processing branch via the switching stage 3 to the input 2 (via the input amplifier 1). At this time, the data lead 20 can be similarly connected to the switching stage 3. Further, the oscillation generator 16-
The frequency of the oscillation generated from 19 is the phase locked loop 16
Adjustable by the data input 21 of. Oscillation generator 1
6 to 19 are also connected to the crystal oscillator 22 as a frequency reference.

The controllable amplification stages 7, 8, 9 have a control input 23 which makes their gain coefficient controllable. In this case, the controllable amplification stages 7, 8, 9 can be adopted in the control loop for amplitude control or power control of the RF signal.

The data lead 20 and the phase locked loop 16
The data input 21 can be connected to the control unit (not shown) of the receiving operation of the tuner.

The filter stages 4, 5, 6 are connected to the lead 24 of the phase locked loop 16. A signal for frequency selection by the oscillation generators 16 to 19 can be supplied through the lead portion 24 by a conventional method. In particular, the tuning diodes of the filter stages 4, 5 and 6 are connected to the oscillation stage 1
Synchronize in the same manner as 7, 18, and 19.

FIG. 1 also shows what is included in the tuner embodiment already described in the RF signal processing unit of the video recorder. To this end, FIG. 1 shows that the input section connects to the antenna input section 26 of the video recorder and the
Shown is another input amplification stage 25 connected to the input 2 of the signal tuner. The input unit 2 is also connected to the input unit of the RF signal superimposing stage via the bridging amplifier 27. The output section constitutes the antenna output section 29 of the video recorder.

Input unit 30 for baseband video signal
Constitutes the first input of the low frequency signal superposition stage 31.
The input 32 for the audio signal is connected to the audio signal modulation stage 33. This stage is connected to the second input of the low frequency signal superposition stage 31. In the audio signal modulation stage 33, the input section 32
The audio signal supplied from the sub-carrier is modulated on the sub-carrier oscillation, and thereafter, in the low frequency signal superimposing stage 31, it is additively superimposed on the baseband video signal from the input unit 30. In this way, the FBAS signal is generated and the FBAS signal is supplied through the output section of the low frequency superposition stage 31. The output section 34 is connected to a modulation stage 35 and the FBAS signal is up-converted using one of the oscillation stages, here the oscillation stage 19 of the third signal processing branch. An RF signal is generated at this time and is supplied to the RF signal superposition stage 28 and further to the antenna output 29 of the video recorder.

In FIG. 1, the elements surrounded by dashed line 36 are preferably coupled to an integrated group of components. Similarly, the element surrounded by the alternate long and short dash line 37 can be connected to an integrated group of other components. These collection groups
In particular, it can be integrated on a semiconductor body.

FIG. 2 shows a second embodiment according to the present invention. Compared to the embodiment of FIG. 1, the wideband input amplifier 1 is replaced by a wideband controllable input amplifier 38 which in this case is connected to a control input 23 for RF signal amplitude and power control. By contrast, the controllable amplification stages 7, 8, 9 are omitted in the signal processing branch, and in the variant of FIG. 2 other signal amplifications or return losses are desired at these positions in the circuit arrangement. It can be replaced by an amplification stage having a constant gain factor.

In another respect, the embodiments illustrated in FIGS. 1 and 2 correspond to each other.

These tuners are particularly suitable for use in the RF processing stage of satellite tuners and video recorders.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a tuner according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a tuner according to the present invention.

[Explanation of symbols]

 1 Wideband Input Amplifier 2, 30, 32 Input Section 3 Switching Stage 4, 5, 6 Filter Stage 7, 8, 9 Controllable Amplification Stage 10, 11, 12 Mixer Stage 13 Node 14 Output Amplifier 15 Common Output Unit 16 Phase Locked Loop 17, 18 and 19 Oscillation stage 20 Data lead 21 Data input 22 Crystal oscillator 23 Control input part 24 Lead part 25 Input amplification stage 26 Antenna input part 27 Bridge amplifier 28 RF signal superposition stage 29 Antenna output part 31 Low frequency signal superposition stage 33 Audio signal superimposing stage 34 Output section 35 Modulating stage 36 Dashed line 37 Dash-dotted line 38 Wideband controllable input amplifier

Claims (7)

[Claims] 1. At least one signal processing branch for frequency selective reception, amplification and / or frequency conversion of an RF signal by a wide band input amplifier, and an RF signal which can be supplied from an input via the input amplifier. A switching stage that can be optionally passed through one of the processing branches, each signal processing branch having a filter stage connected to the switching stage;
A controllable amplification stage arranged subsequent to the filter stage and a mixer stage following the amplification stage, wherein the output of the mixer stage is connected to a common output branch via a signal coupling unit. And the tuner. 2. A wideband controllable input amplifier for at least one signal processing branch for frequency selective reception, amplification and / or frequency conversion of an RF signal, and an RF signal which can be supplied from an input via said input amplifier. A switching stage that can be optionally passed through one of the signal processing branches, each signal processing branch comprising a filter stage connected to the switching stage and a mixer stage; The output of the mixer stage
A tuner characterized in that it is connected to a common output branch via a signal coupling section. 3. The tuner according to claim 1, wherein the mixer stages of all the signal processing branches are connected to a common oscillation generator. 4. The tuner of claim 3, wherein the oscillator generator comprises a common phase locked loop and a separate oscillator stage for each signal processing branch. 5. Tuner according to claim 1, when dependent on claim 1, characterized in that, together with the oscillation generator, the controllable amplification stages and mixer stages of all signal processing branches are combined in an integrated component. 6. Tuner according to claim 4 or 5, characterized in that the input amplifier and the switching stage are coupled to an integrated component. 7. A tuner as claimed in claim 4, when dependent on claim 2, characterized in that, together with the oscillator generator, all signal processing branch mixer stages are coupled to an integrated component.